The present invention relates to method for managing subscriber location information in a mobile communications system. When a mobile subscriber moves to another place, registration notification is carried out from a visitor location register(hereinafter, referring to VLR) to a home location register(HLR). In case that request for the registration notification and call processing procedure about the same subscriber is overlapped, the HLR protects multi-location registrations about the same subscriber until a previous registration notification is completed. Thereby, this invention relates to method for managing subscriber location information in a mobile communications system, for always maintaining a location information about a subscriber in a HLR and a VLR, correctly.
Generally, a digital mobile communications system using CDMA(Code Division Multiple Access) comprises a home location register(HLR) and a visitor location register(VLR). The HLR has a database for managing extra service information, location information, and etc., about mobile subscribers. The VLR is used by a mobile exchanges to search information which processes a call from/to subscriber visiting area. Accordingly, the HLR should maintain exact information about a plurality of subscribers. And also, the HLR should maintain temporary information in the single VLR only, in which the information is generated according as subscribers move.
However, there is no regulation about a concrete situation in a current mobile communications standard(IS-41-C). So, when other mobile network subscribers try to call, it is frequently disconnected because the HLR could not offer subscriber information, correctly.
FIG. 1 is a flow chart showing a registration notification(RN) procedure of a normal mobile subscriber. It tells a case that a mobile station(MS1) moves from a previous service system area(where a first visitor location register VLR1 exists) to a new service system area(where a second visitor location register VLR2 exists).
After the VLR2 senses the MS1 and sends a registration notification invoke(RNI) message of the MS1 to the HLR according as the MS1 moves(ST1), the HLR updates and saves a location of the MS1 in database. Here, the VLR1 has a subscriber record of the MS1. The HLR thus requests the VLR1 to erase location information of the MS1(ST2). And then, VLR1 erases the subscriber record of the MS1 stored in the current database, and sends a registration cancellation return result(RCRR) message of MS1 to the HLR(ST3). After receiving the message for erasing location, the HLR sends a registration notification return result(RNRR) message of the MS1 to the VLR2(ST4). Accordingly, the VLR2 may create a subscriber record of the MS1 in the database.
FIG. 2 is a flow chart showing a call processing procedure of a mobile subscriber. In case that a calling party""s MS requests the desired called party""s mobile station(MS2) to call in which the MS2 is in other service system area, the FIG. 2 shows the procedure among a calling party""s mobile switching center(MSC) and the HLR and a called party""s mobile switching center(MSC1).
When the calling party""s MS requests the MS2 to call, the corresponding MSC of the calling party""s MS sends a location request (LR) message of the MS2 to the HLR(ST11). The HLR which received the LR message from the MSC, sends a routing request (RR) message of the MS2 to a corresponding MSC1 via VLR1 of the MS2 in order to know routing information of the MS2(ST12). The called party""s MSC1 receives the RR message and allocates routing information TLDN(temporary local directory number). At this time, the VLR1 has a subscriber record of the MS2. In case of receiving the TLDN of the MS2, the MSC1 sends a routing request return result(RRRR) message of the MS2 to the HLR(ST13). The HLR which received the RRRR message sends a location request return result(LRRR) message of the MS2 to the calling party""s MSC(ST14).
Hereinafter, a call processing procedure of a mobile subscriber will be explained in case that the HLR has incorrect location information of the MS2 with unrecognized reasons.
First, the calling party""s MSC sends a location request invoke(LRI) message of the MS2 to the HLR, showing in below of FIG. 2(ST21). The HLR sends a routing request (RR) message to the VLR1 of the MS2 in order to know location information of the MS2(ST22). Here, the VLR1 does not have the subscriber record of the MS2. Accordingly, the VLR1 sends an error code as well as routing request(RR) error message of the MS2 to the HLR, in which the error massage indicates that the subscriber can not be recognized(ST23).
Here, the HLR clears the subscriber location information stored in the HLR database(ST24). And then the HLR sends a location request return result(LRRR) message with an access denied reason parameter of the MS2 to the calling party""s MSC. As a result, the call is failed.
In case that a mobile station(MS3) moves to a new serving area, location information of the subscriber is registered on at least two VLRs, respectively. And it will be now explained in FIG. 3 showing a registration notification(RN) flowchart of a mobile subscriber.
When a mobile station(MS3) moves to a new serving area, the VLR2 in a new serving area senses the MS3 and requests the HLR a first registration notification invoke(RNI) of the MS3(ST1). The HLR updates the location of the MS3 and stores a previous location on database. Here, the VLR1 still has the subscriber record of the MS3. Accordingly, the HLR requests the VLR1 registration cancellation(RC)of the MS3(ST2).
But, in case that the VLR2 requests the HLR a second RNI(ST3), the HLR answers about a registration notification request(RNR) without any registration cancellation(RC) procedure because it""s from a current service system, again. Accordingly, the HLR sends a second registration notification return result(RNRR) message of the MS3 to the VLR2(ST4). Consequently, a subscriber record of the MS3 is created in the VLR2.
Besides, in case that a registration cancellation request(RCR) of the MS3 requested by the HLR to the VLR1, is not carried out because the MS3 is busy, and etc., the VLR1 sends a registration cancellation return result(RCRR) message with a cancellation denied parameter to the HLR(ST5). Because the RCR of the MS3 is denied, the HLR restores a location information of the database and sends a first RNRR message with an access denied reason parameter to the VLR2 in order to re-register the location of the MS3 in the VLR1 where the previous service system is provided (ST6).
The HLR is operated in the same way when the answering information is lost in the step (ST2 or ST5). Even though a first registration notification(RN) of the MS3 failed, the database of the VLR2 already has the subscriber record of the MS3 by requesting the second RN(ST3) and also, the subscriber record which established in the database of the VLR1, was not canceled. Consequently, both visitor location registers VLR1, VLR2 have a subscriber record of the MS3.
Like this way, when the other mobile subscriber tries to call, the HLR can not carry out a normal call processing because the HLR and VLR have incorrect information about a corresponding subscriber.
FIG. 4 shows a signal processing flowchart for explaining errors. The errors may be happened in case that a registration notification(RN) and call processing procedures about same mobile subscriber are overlapped showing in FIG. 1 to FIG. 2, when a mobile station(MS4) moves to another serving area.
In case that the MS4 moves to a new serving area, a VLR2 senses the MS4 and requests a registration notification invoke(RNI) to the HLR(ST31). The HLR updates the location of the MS4 and stores the previous location in database. The VLR1 has a subscriber record of the MS4. And then the HLR requests the VLR1 a registration cancellation(RC)of the MS4(ST32). Therefore the VLR1 erases the subscriber record of the MS4.
Here, when the subscriber record of the MS4 is normally erased in the VLR1, the VLR1 sends a registration cancellation return result(RCRR) message to the HLR(ST38), in which the message tells that the subscriber record of the MS4 is erased. The HLR finally sends a registration notification return result(RNRR) message which requested by the VLR2, to the VLR2(ST39). And the VLR2 creates the subscriber record of the MS4 in the database.
But, there is a situation that a location request (LR) message of the same MS4 above is sent from a mobile switching center(MSC) which does not request a registration notification(RN) before the RN requested from the VLR2 is not completed normally(ST33). In above situation, the HLR tries to receive a temporary local directory number(TLDN) by sending a routing request(RR) message to a new service system(ST34), because the location information of a corresponding subscriber, which is stored in the HLR database, is already updated to the information of a new service system. But, the VLR2 does not have the subscriber record of the corresponding MS4 because the RN of the MS4 is processing in the current new service system. Accordingly, the VLR2 sends the RR error message of the MS4 to the HLR as an answer of the RR(ST35). And then, the HLR, received the error message, clears the subscriber location information of the MS4 of the database(ST36). The HLR then sends the location request return result(LRRR) message to the MSC(ST37).
Here, there is another situation that a location request invoke(LR) message of the MS4 is sent from a MSC to the HLR by called signal request of the same MS4 above(ST40). In this case, the HLR has already cleared the location information of the MS4 by receiving the routing request(RR) error message in the step(ST36). Consequently, the HLR does not have the subscriber location information of the MS4. Accordingly, the call is failed by sending the location request return result(LRRR) message with access denied reason of the MS4 to the corresponding MSC where requested the location information(ST41).
Additionally, the VLR1 sends the registration notification invoke(RNI) message of the MS4 to the HLR in case that the MS4 moves to another serving area (explained by drawings as an example, the MS4 moves to an area where the VLRL manages)(ST42).
But, because the subscriber location information of the MS4 is already cleared in the HLR database, the registration cancellation(RC)is not requested to the VLR2 of the previous serving area. And by sending the registration notification return result(RNRR) message of the MS4 to the VLRL (ST43), the VLRL creates a subscriber record of the MS4 in the VLR1 database.
The VLR2 already has the subscriber record of the MS4, therefore does not request the registration notification(RN) to the HLR in case that the MS4 moves to a serving area where has a current subscriber record(explained by drawing as an example, the MS4 moves to an area where the VLR2 manages). Accordingly, it is easy to fail when the other mobile subscriber try to call because the HLR is managing an incorrect subscriber location information of the MS4.
In above case, there is no way that a user of the corresponding mobile station(MS) can check the reason of disconnection except calling to a mobile communications company. And a VLR operator should select and erase useless subscriber records in the VLR database. But, the way to solve like above is not the essential solution and there are possibilities that the same problem happens successively.
Thus taking the above-mentioned problems into consideration, a first objective of the present invention is to solve the problems in method for managing subscriber location information in a mobile communications system, as described above, by maintaining correctly temporary information of the same subscriber in a single VLR only by a HLR, when two VLRs request the HLR registration notification as overlapped, in case that a mobile station moves from a previous serving area to other area.
A second objective of the present invention is to provide a method for managing subscriber location information in a mobile communications system, in which a HLR maintains currently a correct location of a corresponding subscriber when a registration notification(RN) and call processing procedure of the same subscriber are happened by overlapped.
According to an embodiment to achieve the first object of the present invention, a method for managing subscriber location information in a mobile communications system, comprising processes of carrying out a corresponding registration notification(RN) of a mobile station(MS) in a HLR and indicating that the registration notification(RN) is processing when the MS moves to a previous serving area, and preventing multi-location registrations about a same subscriber during handling a registration notification(RN).
According to another embodiment to achieve the first object of the present invention, a method for managing subscriber location information in a mobile communications system, comprising processes of carrying out a corresponding registration notification(RN) of a MS in a HLR and in a corresponding VLR that the registration notification(RN) is processing when the MS moves to a new serving area, and preventing multi-location registrations about a same subscriber during handling a registration notification(RN).
According to the other embodiment to achieve the second object of the present invention, a method for managing subscriber location information in a mobile communications system, comprising processes of carrying out a corresponding registration notification(RN) of a MS in a HLR and indicating that the registration notification(RN) is processing when the MS moves to a new serving area and ignoring multi-location registration signals about a same subscriber and a call processing signal from an exchange during registering the location until a previous registration notification(RN) is erased.
According to a 4th embodiment to achieve the second object of the present invention, a method for managing subscriber location information in a mobile communications system, comprising processes of carrying out a corresponding registration notification(RN) of a MS in a HLR and indicating in a corresponding VLR that the registration notification(RN) is processing when the MS moves to an area where a new service system is provided, and ignoring multi-location registration signals about a same subscriber and a call processing signal from an exchange during registering the location until a previous registration notification(RN) is erased.